[Problem to be Solved] Provided is a method for evaluating a flavor-improving agent that can efficiently and objectively evaluate the flavor-improving effect of a flavor-improving agent noninvasively, low restrictively, in a short time by solving disadvantages of sensory evaluation and other methods. [Solution] The method includes the steps of (1) giving subjects a solution prepared by adding a known flavor-improving agent to an aqueous solution of a taste substance selected from the group consisting of sweet substances, salty substances, acid substances, bitter substances, and umami substances and measuring a change in signal strength at a periphery of the temple of the forehead caused by the drinking of the solution with an apparatus for in vivo optical measurement； (2) selecting a subject showing a change in signal strength at the periphery of the temple of the forehead by the addition of the known flavor-improving agent in the step (1)； (3) giving a solution prepared by adding a test flavor-improving agent to an aqueous solution of the taste substance to the subject selected in the step (2) as an object, measuring a change in signal strength at the periphery of the temple of the forehead caused by the drinking of the solution with an apparatus for in vivo optical measurement, and evaluating the flavor-improving effect from the change in signal strength as an index.
